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TRANSCRIPT
TRB Webinar: Case Studies in Performance Based
Analysis of Geometric Design
June 17, 2015 2:00 PM – 3:30 PM ET
Today’s Panelists and Moderator
• Mike Colety, Kimley Horn [email protected]
• Andy Wolpert, CH2M [email protected]
• April Renard, Louisiana DOTD [email protected]
• Howard Lubliner, Kansas DOT [email protected]
• Richard Porter, University of Utah [email protected]
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DESIGN TO A BUDGET KANSAS DOT TRB Webinar – June 17, 2015
Introduction
Howard Lubliner, P.E., Ph.D. 15 years with Kansas DOT Research in application of the Highway Safety Manual
(HSM) Active in TRB, AASHTO, and NCHRP efforts to research
and promote HSM
Design to a Budget
What is “Design to a Budget”?
How we implemented performance based design to achieve project goals and maintain our budget (K-177 case study)
Lessons learned Kansas DOT implementation of quantitative safety analysis in performance based design
What is “Design to a Budget”?
T-Works is KDOT’s 10-year, $8 billion transportation program passed in 2010
Focused on preservation of existing infrastructure and local input to determine modernization needs
Local Input
Design to a Budget
Unlimited wants with a limited budget KDOT used $150 million to address 5 different
corridors using this methodology Understanding that available funds would not cover
bringing corridors up to full standards Performance based design was used to prioritize
improvements within the selected corridors
Design Methodology
Program Project
Estimate Cost
Design Solution
Purpose & Need
Traditional Method
Design Methodology
Program Project
Estimate Cost
Design Solution
Purpose & Need
Traditional Method Budget Capped
Design Solution
Purpose & Need
Budget Set
Project Programmed
K-177 Modernization
$25 Million Construction Budget 22.9 Mile Corridor
Narrow Shoulders, Steep Side Slopes, Rolling Geometrics
Develop Purpose & Need
Public Input Geometry Operations Safety
Develop Purpose & Need
Public Input Geometry Operations Safety
Develop Purpose & Need
Public Input Geometry Operations Safety
Design Solution
Improve Each Segment
Highest Benefit/ Cost
Geometry Meeting
Standards Advisory
Committee Input
Benefit / Cost Analysis
Used calibrated HSM Crash Prediction Model to quantify crash expectancy for each option Optimized solution had 13% crash reduction across
corridor 25% crash reduction in focus areas
Used TWOPAS model to evaluate operations Increased from 50% to 62% passing opportunity
Design Solution
Lessons Learned
Benefit/Cost safety analyses can augment the design process Especially beneficial for practical improvements /
performance based design Can be used across a wide variety of projects
HSM Crash Prediction Models are an imperfect but valuable tool Feel comfortable to utilize engineering judgement
More Information
FHWA Case Study (K-177) www.fhwa.dot.gov/design/pbpd/case_studies.cfm
Email [email protected]
20 Drive Safe Nevada Zero Fatalities
Zero Fatalities Drive Safe Nevada
21 Drive Safe Nevada Zero Fatalities
HSM Implementation in Nevada NDOT Safety
› Ken Mammen, NDOT Chief Safety Engineer › Jaime Tuddao, NDOT Safety Engineer
Task Force of NDOT Divisions and MPOs Consultant Team – Kimley-Horn
› Mike Colety, Project Manager › Michael Mosley, Project Engineer - IHSDM
22 Drive Safe Nevada Zero Fatalities
Nevada Implementation Schedule NV in fourth year of implementation State and regional staff participating on task force
to guide implementation HSM Practitioners and IHSDM Training taught by
FHWA in 2013 and 2014 HSM can be applied to all transportation projects,
although limitations on data Application of HSM to case studies by HSM
Implementation consultants Focusing on application of HSM to ongoing
projects by agency and staff other consultants
23 Drive Safe Nevada Zero Fatalities
Applying the HSM in Project Development
Source: http:/safety.fhwa.dot.gov/hsm/hsm_mgrsguide/sec3.cfm
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Project Safety Process (PSP)
25 Drive Safe Nevada Zero Fatalities
Nevada Case Studies Planning and Programming
› Project justification (roundabout) Pre-Design and Scoping
› Scoping (two-lane, two-way rural) Design and Construction
› Design exception (freeway)
26 Drive Safe Nevada Zero Fatalities
Project Justification Case Study 5 legged intersection with high crashes based on
AADT Construct 5 legged roundabout to reduce crashes Expected crashes predicted over a 20 year
horizon
27 Drive Safe Nevada Zero Fatalities
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Project Justification - Crash Prediction
Alt. 1
Roundabout
Total 47.1 27.0
Reduction in Total Crashes over Existing Conditions
N/A 20.1
Crash Reduction Factor (CRF) N/A 43%
Existing Conditions
2013-2033 Expected Total Number of Crashes
29 Drive Safe Nevada Zero Fatalities
Project Justification – Substantive Safety Summary BCR was above 1 until
external factors were considered – R/W, new bridges over canals
Safety funds could be spent since proven countermeasure, but alternatives being evaluated
Alt. 1
Roundabout
Total Alternative Cost $4,378,865
Total Annual Benefit including 2% Growth per year
$114,092
Total Annualized Cost $301,173
Benefit-Cost Ratio 0.37Average Annual Net Return ($192,081)
30 Drive Safe Nevada Zero Fatalities
Scoping Case Study Two-lane, two-way rural road connecting Las
Vegas to Lake Mead National Recreation AADT approximately 1,000 vehicles per day 35 total crashes, include 6 fatal crashes in
previous five years (fatal crashes 17% of total) Expected crashes predicted over a 20 year
horizon
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IHSDM Review
32 Drive Safe Nevada Zero Fatalities
Scoping Case Study - Alternatives 1. Add a centerline rumble strip 2. RSA single curve at MP 9 3. Improve substandard superelevation 4. Add a climbing lane westbound from Pabco
Road to top of the hill (MP11.6 to 8.5) 5. Revise both curves at MP 9 6. Widen shoulder to 5’ with rumble strip and
improve roadside condition for entire project
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IHSDM Review
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Scoping - Crash Prediction
Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6CL Rumble
StripRSA Curve
at MP 9Superelevation Improvements
Climbing Lane
New Reverse Curve at MP 9
Widen Shoulder to 5'
Total 90.17 84.76 85.59 89.11 75.93 84.38 65.43Reduction in Total Crashes over Existing Conditions
N/A 5.41 4.58 1.06 14.24 5.79 24.74
Crash Reduction Factor (CRF)
N/A 6% 5% 1% 16% 6% 27%
Existing Conditions
2013 - 2033 Expected Total Number of Crashes
*Alternatives developed independently in the model so that during evaluation they could be, somewhat, combined for decision makers.
35 Drive Safe Nevada Zero Fatalities
Scoping – Crash Severity Project history of crash severity was significantly
different than the HSM default values
36 Drive Safe Nevada Zero Fatalities
Scoping– Societal Crash Cost by Severity Benefit dollar amounts are calculated by
multiplying the societal cost of crashes saved. Nevada 2012 Societal Costs
› FATAL $5,339,711.00 › INJURY A $285,349.00 › INJURY B $104,302.00 › INJURY C $59,037.00 › PDO $9,638.00
37 Drive Safe Nevada Zero Fatalities
Scoping – Cost Calculations
Each alternative cost was estimated using the NDOT Estimating Wizard
37
SECTION TOTAL
SECTION I - ROADWAY CONSTRUCTION $777,402
SECTION II - BRIDGES
SECTION III - WALLS
SECTION IV - TYPICAL INTERCHANGES
SECTION V - SIGNAL SYSTEMS AT INTERSECTIONS
SECTION VI - DEMOLITION $65,902
SECTION VII - ADDITIONAL ITEMS $843,490
SECTION VIII - STANDARD PERCENTAGE ADDERS $428,125
TOTAL PRESENT DAY CONSTRUCTION COST $1,271,615
TOTAL CONSTRUCTION COST $1,309,763
TOTAL CONSTRUCTION & ENGINEERING $1,474,704
SECTION IX - RIGHT-OF-WAY (ROW) COSTS
SECTION X - ENVIRONMENTAL CONSIDERATION COSTS
GRAND TOTAL PROJECT COST $1,474,704
CURRENT ESTIMATE LOW RANGE HIGH RANGE
TOTAL CONSTRUCTION COST $1,309,763 $1,000,000 $2,000,000
TOTAL PROJECT COST $1,474,704 $1,000,000 $2,000,000
Estimate prepared by: Michael MosleyDate of initial estimate: December 7, 2012Date of latest estimate revision: December 10, 2012Route name or number: SR 147 - MP 7.38 to MP 14.33Project Title: Revised RSA Curve at MP 9Project length (in miles): 6.95District price database used: District 1 1Predominant County: Clark 3
2013
ESCALATED TO YEAR
2013
2013
2013
Revised RSA Curve at MP 9PREPARED BY THE NEVADA DEPARTMENT OF TRANSPORTATION
ESTIMATED PROBABLE CONSTRUCTION COST
38 Drive Safe Nevada Zero Fatalities
Scoping – Benefit- Cost Ratio Calculation
38
BENEFIT-COST RATIO (BCR)(2012 DOLLAR FIGURES) 01/22/13
ENGINEERING AUTHORIZATION NO. Not KnownPROJECT NO. 2028PROJECT LOCATION SR 147 - MP 7.4 to MP 14.3
ALTERNATIVE NO.COUNTERMEASURE
AADT - Segment or Main St & Cross St SEGMENT
ROADWAY CHARACTERISTICS 2 LANE UNDIVIDED
DEMOGRAPHIC DESIGNATION RURAL ----------------------FUNCTIONAL CLASSIFICATION 3 OTHER PRINICPLE ARTERIAL
IMPLEMENTATION COSTS $1,474,704.14ANNUAL MAINTENENCE COSTS $5,000.00CURRENT PRIME INTEREST RATE 3.25%PERCENTAGE OF GROWTH 2.00%ESTIMATED SERVICE LIFE &NUMBER OF YEARS PREDICTED 20 YEAR(S)
5 YEAR(S)
CALCULATION OF REDUCTIONS USING IHSDMIHSDM (Interactive Highway Safety Design Model)http://www.ihsdm.org/
EXSITING CONDITION ALTERNATIVEPRESENT EXPECTED EXPECTED EXPECTED CRASHES SAVEDCRASHES CRASHES CRASHES CRF (%) ANNUALLY
2012 CRASH (A) (B) (C) (D) (E)COSTS
FATAL $5,339,711.00 6 15.5 14.7 5% 0.04INJURY A $285,349.00 4 10.3 9.8 5% 0.03INJURY B $104,302.00 6 15.5 14.7 5% 0.04INJURY C $59,037.00 6 15.5 14.7 5% 0.04PDO $9,638.00 13 33.5 31.8 5% 0.09
CALCULATION OF BENEFITS CRASHES SAVED SOCIETAL SOCIETALANNUALLY COST BENEFIT
(E) (F) (G)
FATAL 0.04 $5,339,711 $209,622INJURY A 0.03 $285,349 $7,468INJURY B 0.04 $104,302 $4,095INJURY C 0.04 $59,037 $2,318PDO 0.09 $9,638 $820
TOTAL ANNUAL BENEFITS (Summation of Column E) $224,322TOTAL ANNUAL BENEFITS (Including Growth ) $228,808CAPITAL RECOVERY FACTOR 0.0688ANNUALIZED IMPLEMENTATION COSTS $101,429TOTAL ANNUALIZED COSTS $106,429AVERAGE ANNUAL NET RETURN $122,380BENEFIT/COST 2.15
PROJECT SAFETY PROCESS
Alt 2Revise single curve at MP 9 per RSA recommendation (1700-foot curve), includes roadside improvements at location.
NUMBER OF YEARS OF CRASH HISTORY DATA
PREDICTIVE METHOD
BCR = PVbenefits PVcosts
› PVbenefits = Present
value of project benefits
› PVcosts = Present value of project costs
39 Drive Safe Nevada Zero Fatalities
Scoping - Substantive Safety Summary
Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6CL Rumble
StripRSA Curve
at MP 9Superelevation Improvements
Climbing Lane
New Reverse Curve at MP 9
Widen Shoulder to 5'
Total Alternative Cost
$65,693 $1,474,704 $945,031 $5,696,473 $2,357,871 $12,113,656
Total Annual Benefit including 2% Growth per year
$270,273 $228,808 $52,956 $711,404 $289,258 $960,195
Total Annualized Cost
$9,518 $106,429 $69,998 $396,797 $167,172 $838,164
Benefit-Cost Ratio
28.40 2.15 0.76 1.79 1.73 1.15
Average Annual Net Return
$260,755 $122,380 ($17,043) $314,607 $122,086 $122,031
$12,126,998
$1,235,964
$834,081
1.47
$396,883
40 Drive Safe Nevada Zero Fatalities
Design Exception Case Study
Adding a climbing lane › AADT = 18,000 vpd › Facility type is Freeway › 10’ Shoulder standard not met with additional
lane
41 Drive Safe Nevada Zero Fatalities
Design Exception Case Study
Proposed Exception is a 2 foot right shoulder at bridge pier
42 Drive Safe Nevada Zero Fatalities
I-15 Logandale TI Design Exceptions– Pilot Project
42
Design Exception Case Study
43 Drive Safe Nevada Zero Fatalities
Design Exception Case Study
44 Drive Safe Nevada Zero Fatalities
Design Exception - Alternatives Alternative 1:
› Replace the existing bridge with a new bridge and piers outside the clear zone
Alternative 2: › Narrow the median and shift the lanes more to the
inside. This will cause the need for a 2000 foot long retaining wall to be constructed and a barrier to be added to the inside of the NB lanes in the median.
Alternative 3: › Narrow the right shoulder to 2 feet for 30 feet
using a taper from 10’ to 2’ of 176’
45 Drive Safe Nevada Zero Fatalities
Design Exception - Variables
Alt. 1 Alt. 2 Alt. 3
New Bridge Median Narrowing
Shoulder Narrowing
Left Shoulder Width 4' 4' 4' 4'
Right Shoulder Width 8' 10' 10'
2' for 30 feet and
176' taper
Median Traversable Traversable Non-Traversable Traversable
Median Width 28' 28' 20' 28'Median Barrier SB Only SB Only NB and SB SB Only
Outside Barrier Rt 16' Rt N/A 10'Rt 2' (Follows Shoulder)
12' Climbing Lane No Yes Yes Yes
Analysis Variables
Existing Conditions
46 Drive Safe Nevada Zero Fatalities
Design Exception – Substantive Safety Summary
Results Alt. 1 Alt. 2 Alt. 3
New Bridge Median Narrowing
Shoulder Narrowing
Total 90.1 85.5 89.5 86.9Reduction in Total Crashes over Existing Conditions
N/A 4.6 0.6 3.1
Crash Reduction Factor (CRF) N/A 5.1% 0.7% 3.5%
Total Alternative Cost N/A $2,750,000 $1,500,000 $100,000
Total Annual Benefit including 2% Growth per year
N/A $25,884 $3,406 $17,653
Total Annualized Cost N/A $199,142 $113,168 $16,878
Benefit-Cost Ratio N/A 0.13 0.03 1.05Average Annual Net Return N/A ($173,258) ($109,763) $775
2013-2033 Predicted Total Number of Crashes
Existing Conditions
QUANTIFYING THE SAFETY EFFECTS OF VARIOUS DESIGN ALTERNATIVES IN NEPA
April Renard, P.E. Highway Safety Manager Louisiana Department of Transportation & Development
PROJECT OVERVIEW Alternative N-S
corridor to I-12 Louisiana
Revised Statute 47:820.2B(e)
4-lane arterial Limited access
facility
I-12 TO BUSH PROPOSED ALTERNATIVES No Build Alternative B/O Alternative J Alternative P Alternative Q
ALTERNATIVE SELECTION CRITERIA Land Use Water Resources Ecological Resources
Land cover Wildlife Sensitive habitats T&E species Wetlands
Geology and Soils Air Quality Noise
• Recreational Resources • Traffic and
Transportation – Access – Operations – Safety
• Utilities • Socioeconomics • Aesthetic and Visual
Resources • Cultural Resources • Hazardous and Toxic
Substances
ALTERNATIVE SELECTION CRITERIA Land Use Water Resources Ecological Resources
Land cover Wildlife Sensitive habitats T&E species Wetlands
Geology and Soils Air Quality Noise
• Recreational Resources • Traffic and
Transportation – Access – Operations – Safety
• Utilities • Socioeconomics • Aesthetic and Visual
Resources • Cultural Resources • Hazardous and Toxic
Substances
SAFETY Goal: Quantify the perceived safety benefits from
constructing the project. Presumption: Traffic diverted from existing
roadways with lesser design standards to proposed alignment with higher design standards will result in a reduction in crashes.
Methodology: HSM Predictive Method using IHSDM
IHSDM SOFTWARE Interactive Highway Safety
Design Model Developed in coordination with
TRB, AASHTO and FHWA Decision-support tool;
evaluates safety and operational effects of geometric design decisions on highways
Incorporated HSM Predictive Method in 2010
AREA OF ANALYSIS
Existing routes Proposed
alignments
DATA REQUIREMENTS Horizontal curvature Vertical curvature Cross sectional elements
Number of lanes and lane width
Shoulder width and type
Cross slope Roadside foreslope Median width and
type
ADT Design Speed Driveway Density Roadside Hazard
Ratings Intersections
• Traffic control • Skew angle • Turn lanes
DATA RESOURCES Highway Needs Database Surface Type Log File Data Collection/Management Systems As-builts and Plans LandXML files* Google Earth Planning models (Transcad, REMI)
STUDIED SECTIONS
US 190 US 190 Business LA 21 LA 59 LA 36 LA 435 LA 41 LA 434 US 11 4 Alternatives
PREDICTED NUMBER OF CRASHES Route Control Section No Build Alt B/O Alt J Alt P Alt Q 1a US 190 013-11 478.44 463.41 468.03 464.58 472.14 US 190-X 013-10 27.54 26.17 26.33 26.25 26.84 LA 21 030-01 88.49 97.14 67.84 46.16 70.52 594.47 586.72 562.2 536.99 569.5 1b LA 59 281-03 84.7 70.77 80.64 76.07 80.66 LA 36 280-01 16.37 15.76 15.44 15.2 15.28 LA 59 852-09 17 11.84 14.32 12.76 11.68 LA 21 030-01 75.72 58.52 37.26 22.7 38.77 193.79 156.89 147.66 126.73 146.39 1c LA 59 281-03 84.7 70.77 80.64 76.07 80.66 LA 435 281-04 29.31 26.29 28.86 41.24 30.57 LA 41 058-02 28.98 24.62 3.22 2.98 3.18 142.99 121.68 112.72 120.29 114.41 2 US 11 018-04 28.69 27.89 25.72 27.42 27.63 LA 41 058-01 91.38 81.12 36.64 61.64 50.74 LA 41 058-02 28.98 24.62 3.22 2.98 3.18 149.05 133.63 65.58 92.04 81.55 3 LA 434 852-12 7.09 4.45 5.6 5.24 5.43 LA 36 280-03 10.11 9.9 12.02 10.93 24.43 LA 41 058-01 53.67 45.87 11.75 30.44 14.58 LA 41 058-02 28.98 24.62 3.22 2.98 3.18 99.85 84.84 32.59 49.59 47.62 4 Proposed Alternative 0 43.58 43.5 30.37 32.5 TOTAL NETWORK CRASHES 1180.15 1127.34 964.25 956.01 991.97
DISTRIBUTION OF CRASHES
Severity LA (all) LA (rural 2-lane) HSM (rural 2-lane)
Fatal 0.44% 2.08% 1.30%
Severe 0.83% 1.08% 5.40%
Moderate 6.15% 10.59% 10.90%
Possible Injury 21.70% 30.92% 14.50%
PDO 70.89% 55.33% 67.90%
100.00% 100% 100.00%
COST OF CRASHES
Severity Cost per Person
Cost per Person (w/ Loss of
Quality of Life)
Fatal $1,241,054 $4,275,313
Severe $917,127 $1,990,456
Moderate $160,602 $299,823
Possible Injury $7,953 $10,782
PDO $3,216 $3,216
OVERALL COMPARISON
Rank Alternative Total Network
Crashes Reduction in
Crashes Total Cost of
Crashes* Reduction in Cost
1 P 956.01 224.14 $25,693,587.03 $6,023,954.35
2 J 964.25 215.9 $25,915,044.08 $5,802,497.30
3 Q 991.97 188.18 $26,660,042.81 $5,057,498.57
4 B/O 1127.34 52.81 $30,298,227.43 $1,419,313.95 5 No Build 1180.15 0 $31,717,541.38 $0.00
*Louisiana crash distribution and cost estimates (do not include pain and suffering)
Rank Alternative Total Network
Crashes Reduction in
Crashes Total Cost of
Crashes* Reduction in Cost
1 P 956.01 224.14 $55,592,679.06 $13,033,904.54
2 J 964.25 215.9 $56,071,841.07 $12,554,742.53
3 Q 991.97 188.18 $57,683,779.29 $10,942,804.31
4 B/O 1127.34 52.81 $65,555,643.57 $3,070,940.03
5 No Build 1180.15 0 $68,626,583.60 $0.00
*Louisiana crash distribution and cost estimates (includes pain and suffering)
RECORD OF DECISION Alternative P
Safety Alternative Q
Environmental
Crash Prediction for Freeways and Interchanges Using the Interchange Safety Analysis Tool – Enhanced (ISATe)
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
We ought to understand the expected safety performance of a $250 million investment
Would you expect these three alternatives to experience the same number of crashes over a 30 year project life? If not, would it be helpful to understand the potential differences when selecting a preferred alternative?
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
High value ISATe applications to typical planning and design issues
Predict crashes before and after reconstruction of a corridor Evaluate effect of adding new interchange Evaluate effect of increasing capacity of an existing corridor
through widening Evaluate effect of increasing or decreasing weaving distance Compare performance of CD vs. mainline weaving vs ramp braid
solutions Predict and compare the safety performance of interchange
configuration alternatives Evaluate and refine preliminary geometry Evaluate and document design exceptions
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Limitations
Site types not addressed – Facilities with HOV lanes – Freeways with managed lanes separated by a buffer – Ramp metering – Frontage roads – Speed change lanes at crossroads
Geometric elements not addressed – Vertical geometry – > 10-lane freeway segments – > 2-lane ramp segments – Differing barrier types (i.e. cable barrier vs. jersey barrier) – Single point diamond intersection configuration – Roundabout ramp terminal intersections – Diverging Diamond interchange (Double Cross-Over)
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
The ISATe Model and Tool
Excel Spreadsheet – Input
• Individual site – Freeway segment – Ramp or CD road segment – Crossroad ramp terminal
• Freeway facility • Segmentation is key!
– Output • Crashes for entire facility • Crashes by component • Distribution of crashes
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Case Study: I-270/US 33: Dublin, OH
Interchange is unique Operates as a service interchange to the east as it approaches the Frantz
Road/Post Road intersection Operates as system interchange to the west
LOCAL ROADWAY
FREEWAY SYSTEM
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Project Application – I-270/US 33 Interchange
Goals • Improve Safety • Address Traffic Congestion • Resolve Obsolete Geometric Designs • Fiscal responsibility o Develop phased plan to meet funding constraints
Three alternatives further studied and developed • Alternative 4 • Alternative 7 • Alternative 8
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
I-270/US 33 Improvements: Alternative 4
Directional turbine interchange
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
I-270/US 33 Improvements: Alternative 7
Parclo ‘A’ interchange
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
I-270/US 33 Improvements: Alternative 8
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Crash Analysis, 2015-2035 Crash Predictions
ISATe for the I-270/US 33 Interchange – The model was uncalibrated as used – The results used for comparisons are relative – Focused on KAB type crashes from 2015-2035
• Most important crash types • Reliability of data is greater
– Safety was one of many criteria used to determine the preferred alternative
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Results
Total KAB predicted crashes 2015-2035 – Existing: 308 crashes – Alt. 4: 323 crashes – Alt. 7: 360 crashes – Alt. 8: 320 crashes
Societal costs 2015-2035 – Existing: $97M – Alt. 4: $90M – Alt. 7: $102M – Alt. 8: $88M
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Interpretation
Trade-off of reconfiguring interchanges with high speed ramp designs – Increases VMT
‘Higher quality’ design – Safety performance is better even though VMT is 30%
greater than existing
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Alternative 8 – Preferred Alternative (Phase 2)
PHASE 2 CONSTRUCTION (in 10-15 years)
REMOVE LOOP RAMP
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Loop Ramp Crash Prediction
ISATe used to predict ramp KAB type crashes from 2015 to 2025 – Option 1 – Maintain existing ramp with a 230’ radius – Option 2 – Reconstruct ramp with a 200’ radius – Option 3 – Reconstruct ramp with a 185’ radius
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Loop Ramp Crash Prediction
Per the HSM, comparing the predicted crashes is the appropriate approach for the analysis
Using an uncalibrated model is an accepted analysis method
From HSM work in Ohio, the KAB crashes are very close to model predictions
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Summary
Model predicts that the KAB crashes for the options are anywhere from 9-10 crashes on the ramp proper over a 10 year period – Little difference between the options as far as crash
performance Because weaving movements are removed, the
main issue will be the speed entering the ramp curve – Speed will have a significant influence on safety
performance regardless of option
Copyright 2013 by CH2M HILL International, Ltd. • Company Confidential
Summary
Existing ramp radius will be maintained for the project – Treatments will be implemented to slow traffic on the
approach – These countermeasures (or lack thereof) would be
expected to have a more appreciable influence on expected crash performance than the ramp radius
Questions and Discussion